Forum Discussion
MiyuEmi There's no legitimate way to run an EA App-based install without opening the App itself. One thing that may help though is putting the EA App in offline mode. You do have to be online first to put it in offline mode, but you can then leave it running in the background for a while without going back online.
The next time the Store content uninstalls itself, try repairing the game (EA App > Sims 3 > Manage > Repair) rather than reinstalling. It should accomplish the same thing in much less time. And you can also delete the SigsCache folder in Documents > Electronic Arts > The Sims 3; this helps some of the time.
If you do ever decide to buy the game from Steam, you'd need to reinstall your Store content one time, but after that, it should be stable. I've had a Steam install and have never had my Store stuff corrupt aside from a couple of confirmed user errors on my part. That doesn't do anything for the extra cost of the Steam version, and you'd need to register your Steam base game code (preferably on the Sims 3 Store site rather than within the EA App), but it's a viable option if you're frustrated enough.
The link that KevinL5275 provided does work to bypass the launcher, but it still requires you to be signed into the EA App.